For example, as a wiper motor for an automobile, a 3-brush type motor that can switch a rotational speed may be used. In such a motor, an armature on which an armature coil is wound is rotatably disposed inside a cylindrical yoke including a plurality of magnetic poles installed at an inner circumferential surface thereof. The armature has the armature core fitted into and fixed to a rotary shaft from the outside thereof. A slot elongated in an axial direction is formed in the armature core. A plurality of coil in which windings are wound at predetermined intervals according to a distributed winding method are formed in the slot. Each coil is electrically connected to a segment of a commutator attached to the rotary shaft.
Each segment is configured to come in slidable contact with a brush. The brush is constituted by three brushes, i.e., a low speed brush, a high speed brush, and a common brush commonly used with these brushes. The high speed brush is disposed at a more advanced angle than the low speed brush. Then, upon a normal operation, power is supplied by the common brush and the low speed brush, and upon a high speed operation, power is supplied by the common brush and the high speed brush. According to the above-mentioned configuration, in the three-brush type motor, there is a difference in the number of effective conductors in the normal operation and the high speed operation. That is, in the high speed operation, the angle of the motor can be advanced more than in the normal operation and the motor can be operated at a higher number of revolutions than in the normal operation.
However, the motor such as a wiper motor or the like mounted on the vehicle normally needs to be miniaturized due to requirements of improvement of vehicle mountability or the like. For this reason, for example, a motor in which the number of slots of the armature core is set to 16, and the number of magnetic poles is set to 4 is disclosed. In the motor, the coil is wound throughout four teeth according to the number of magnetic poles through the distributed winding method. Then, the coil is connected to the commutator having sixteen segments to which the same electric potentials are short-circuited (for example, see Patent Literature 1).